The right drawer's UI was nonstandard and violated numerous HIG guidelines. This
patch fixes that by doing the following:
- Move the configuration settings to a new page on the stack
- Make the picture/video directory choosers use a common and comprehensible UI
- Don't ask for confirmation before moving items to the trash
- Disable rather than hide inapplicable actions
- Give the back buttons arrows
- Display an informative message when there are no pictures to show
- Fix ellipsis use
- Use correct casing for titles and buttons
- Improve button title formatting and use i18np() where appropriate
- Port a few deprecated uses of Kirigami.Label to the QQC2 version
- Improve header text margins